Cartilage Defect Treatment Using High-Density Autologous Chondrocyte Implantation (HD-ACI)

Abstract

Hyaline cartilage's inability to self-repair can lead to osteoarthritis and joint replacement. Various treatments, including cell therapy, have been developed for cartilage damage. Autologous chondrocyte implantation (ACI) is considered the best option for focal chondral lesions. In this article, we aimed to create a narrative review that highlights the evolution and enhancement of our chondrocyte implantation technique: High-Density-ACI (HD-ACI) Membrane-assisted Autologous Chondrocyte Implantation (MACI) improved ACI using a collagen membrane as a carrier. However, low cell density in MACI resulted in softer regenerated tissue. HD-ACI was developed to improve MACI, implanting 5 million chondrocytes per cm², providing higher cell density. In animal models, HD-ACI formed hyaline-like cartilage, while other treatments led to fibrocartilage. HD-ACI was further evaluated in patients with knee or ankle defects and expanded to treat hip lesions and bilateral defects. HD-ACI offers a potential solution for cartilage defects, improving outcomes in regenerative medicine and cell therapy. HD-ACI, with its higher cell density, shows promise for treating chondral defects and advancing cartilage repair in regenerative medicine and cell therapy.

Keywords: autologous chondrocyte implantation; cell therapy; cultured chondrocytes; high cell density; tissue engineering.

Figure 1

The histological slides stained with hematoxylin–eosin depict regenerated tissue biopsies obtained two years post membrane-assisted autologous chondrocyte implantation (MACI). The sections reveal limited chondrocytes, which are sparsely distributed either in clusters or in specific regions. These chondrocytes are found embedded within a matrix resembling hyaline cartilage. The images are captured at two different magnifications: (A) 200× magnification and (B) 400× magnification.

Figure 2

The hematoxylin–eosin staining provides confirmation of the existence of viable chondrocytes on the surface of all membrane pieces following incubation with varying amounts of chondrocytes, ranging from 1 million to 10 million cells.

Figure 3

Representative histological sections are presented, stained with hematoxylin–eosin (a1–a5) to visualize tissue architecture, and with Safranin-O/Fast Green (b1–b5) to assess the mucopolysaccharide content of the cartilage matrix. The following treatments are depicted: (a1,b1) control, (a2,b2) microfracture, (a3,b3) implant seeded with 1 million chondrocytes per cm², (a4,b4) implant seeded with 5 million chondrocytes per cm², and (a5,b5) implant seeded with 5 million mesenchymal stem cells per cm². Horizontal black bars represent a length of 200 µm [30].

Figure 4

Representative metaphase image from chondrocytes cultured from each cartilage biopsy. The image showcases DAPI-stained nuclei in blue, while the telomeres are visualized as green/white fluorescent signals. The images were captured with the Leica Q-FISH software, using a linear acquisition mode and an integration time of 400 ms to avoid oversaturation of fluorescence intensity. The recordings were made with a COHU CCD camera on a Leica Leitz DMRB fluorescence microscope. Several arrows have been added to indicate the location of some telomeres as an example [32].

Figure 5

Boxplot representation illustrating the progression of International Knee Documentation Committee (IKDC) scores. Our analysis revealed statistically significant differences when comparing all IKDC scores collectively, and pairwise comparisons also reveal statistically significant results. [27].

Figure 6

Box plot representations of the distributions of the visual analogue scale (VAS) (a) and the American Orthopedic Foot and Ankle Society (AOFAS) ankle-hindfoot score (b) at baseline, 12-month, and 24-month follow-up. Each symbol ◦ represents an outlier (data point that significantly deviates from the majority of other data points. The figure highlights statistically significant differences in both parameters across the different time points [36].

Figure 7

EQ-5D-5L score progression is observed in 8 patients with bilateral chondral lesions in the knees (A) and 2 patients in the ankle (B) who underwent treatment with high-density autologous chondrocyte implantation (HD-ACI). The scores are tracked from the baseline visit to the 24-month post-operative period Horizontal bars represent statistically significant pairwise comparison: basal vs. 12 months and basal vs. 24 months (* p < 0.05; ** p < 0.001). [42,43].

Figure 8

High-density autologous chondrocyte implantation (HD-ACI) process. (A) Identification of non-weight bearing regions in the knee or ankle for biopsy extraction. (B) Schematic representation of the HD-ACI approach applied to the knee, comprising two sequential surgical stages: initial biopsy collection, chondrocyte isolation, and culture in the first surgery, followed by the second surgery involving precise placement of cells onto a pre-shaped membrane tailored to fit the lesion’s dimensions and configuration, achieving a cell density of 5 million cells per cm².